Towed linear arrays of receivers have been successfully used in marine operations for both passive and active sonar. At times, a horizontal receiver array is used with a vertical line array of projectors. At other times, the projector array may also be horizontal. In some cases, the horizontal projectors array and horizontal receiver array are linearly arranged on the same tow line. In some cases, the receiver array may be positioned aft of the projector array. In some cases, the receivers may be interspersed with the projectors, such that the arrays are intermeshed.
The natural beam pattern of a linear projector array, when driving all projectors with the same voltage signal, is a narrow focused beam perpendicular to the array, termed the “broadside beam”. In order to insonify a full 360-degrees of azimuthal coverage, the control system driving the projectors tries to “sweep” the natural beam from, for example, a forward end-fire pattern through broadside to an aft end-fire pattern. The beam may be rotated through azimuth by adjusting the timing (phase) of the drive signals for the projectors. The focused nature of the beamwidth places limits on the ping repetition rate.
Similar reference numerals are used in different figures to denote similar components.